In view of the ever growing demands imposed on the organization of high-speed railway travel and due to the increasing payload capacity of railway cars, much attention has been devoted to designing such wheel constructions in which by introducing resilient elements directly into the wheel its dynamic characteristics are greatly improved. Wheels of such a construction may be used in every type of railway vehicle, particularly in trams, subway trains, and railway cars. Such wheels can be employed with the utmost advantage in locomotives.
At present, the most advanced resilient wheel designs are those in which resilient elements have the form of rubber shock absorbers.
In such an arrangement, depending on the type of deformations experienced by the resilient elements, the wheels may be broken down into three groups, the first group including wheels resilient elements of which are subject to compressive strains under the action of vertical loads. These resilient wheels are simple and inexpensive to fabricate, although they suffer from insufficient axial rigidity and excessive radial rigidity, and therefore their efficient application is inherently limited. In addition, when shoe brakes are used, as is the case with most modern locomotives, it is normally very difficult to restrict the influx of heat to the rubber elements of the resilient wheels of the above described construction.
One more type of resilient wheels construction includes resilient elements which experience shearing strains under the action of vertical loads. Such resilient wheels are most popular in the railway transport nowdays. Their use enables to reduce the harmful effect of dynamic impacts on the rails and improve operating conditions both for the wheels and parts and components of the bogie, such as the power transmission of the locomotive, axle boxes, suspension and wheel set axles.
The third group incorporates wheels in which resilient elements are subjected to both shearing and compressive strains under the action of vertical loads. However, these wheels are rather complex in construction and have practically no advantages over the other wheel constructions, due to which they have not been extensively applied in the railroad transport.
For improved operation of the locomotive's bogie having parts and components thereof directly connected to the resilient wheels making up a wheel set, the wheel rigidity, which depends on the geometry, size and construction of the resilient elements, plays an important role.
It is to be especially noted that a reduction in the dynamic impacts to which parts and components of the bogie are exposed depends largely on the correct ratio between the rigidity characteristics of the resilient wheel in the radial and tangential directions, since the radial rigidity influences the dynamic processes of interaction between the resilient wheel and the rail determining the vertical dynamics of the wheel, wheel set axle, axle box, reducing gears and the housing of the traction motor; whereas the tangential rigidity determines the effect of these dynamic processes on the power transmission which includes the traction electric motor, reducer, wheel set axles, and wheels.
There is known a resilient wheel of a railway car comprising a hub with annular projections on the outer surface thereof, and an outer rim having annular projections extending inwardly from the inner surface thereof (cf. West German Pat. No. 2,406,206 IPC B 60b 9/12, published 1975).
Resilient elements of this wheel which are subjected to compressive strains under the action of vertical loads have the form of rectangular plates pressed between the inner surface of the outer rim and the outer surface of the hub, the annular projections serving to restrict axial deformations of the wheel's resilient element.
The above arrangement of the resilient elements provides the wheel with required radial rigidity, thereby maintaining angular velocity of the hub and the wheel set axle rigidly connected thereto, as well as of the reducer and the armature of the traction motor when the wheel dynamically interacts with the rail. This ensures normal operating conditions for the traction motor of the locomotive. At the same time, high radial rigidity of the resilient wheel is caused by insufficient side surface area of the resilient elements, which by virtue of their elastic and shock-absorbing properties fail to sufficiently reduce the action of dynamic loads on the parts and components of the bogie directly connected to the resilient wheel, whereby the travel of the locomotive at high speed will result in that the wheel set axle reducing gears, traction motor and axle boxes may become susceptible to rapid wear and failure.
Also, during extended shoe braking the rolling surface of the wheel's outer rim may heat to as high as 600.degree. C. to cause in the resilient elements in contact therewith a loss of elastic and shock-absorbing properties, because most rubber types are not capable to withstand temperatures in excess of 80.degree. C.
There is also known a resilient wheel of a railway car comprising a wheel hub with an annular projection on the outer surface thereof, and a pressure disk interconnected by bracing elements (cf. West German Pat. No. 1,158,544; IPC B 61f 9/12, published 1964).
Interposed between side surfaces of the annular projection of the hub and pressure disk are inner rim having an annular projection extending from the inner surface thereof and resilient elements having the form of rubber members or blocks reinforced by plates and arranged about the circumference with gaps or spaces therebetween.
The aforedescribed arrangement of the resilient elements imparts required rigidity to the wheel in the radial direction to result in reduced impact loads exerted on parts and components of the bogie and, as a consequence, in their improved operating conditions and extended service life.
However, inherent in the above wheel construction is an excessive tangential rigidity of this wheel caused by the well developed side surface of the resilient element and a rather small thickness thereof. Such a high tangential rigidity of the wheel fails to provide normal operating conditions for the power drive, particularly for the traction motor of the locomotive. In addition, this multiple block construction of the resilient elements of the wheel complicates fabrication of the wheel and shortens its service life.
One more resilient wheel construction is known as exemplified in West German Pat. No. 2,545,032; IPC B 60b 9/12, published 1979. This wheel has a hub and an outer rim.
Resilient elements of this wheel have the form of four rings arranged at an angle to the vertical axis of the cross-section of the wheel; two of these rings engage with the outer surface of the wheel's hub, while two other rings cooperate with the inner surface of the outer rim. Interposed between the two pairs of resilient elements are clamping rings.
This structural arrangement of the resilient elements, while providing the required rigidity in the radial and tangential directions, suffers from a disadvantage residing in that the positioning of one pair of the resilient rings directly on the inner surface of the outer rim results in that during extended shoe braking (with a temperature of the rolling surface of the outer rim up to 600.degree. C.) the rubber of the resilient elements tends to be damaged, thereby affecting the reliability and durability of the resilient wheel.
Another disadvantage resides in that in the resilient wheel of the above construction the pairs of the resilient elements are engaged in succession, which causes an increase in the resonance oscillations of the wheel as a consequence of rail surface irregularities. This in turn results in a less stable travel of the locomotive.
Still another resilient wheel which bears the closest resemblance to the one to be disclosed in this description comprises interconnected by bracing elements and provided with ventilation ports a hub with an annular projection on the outer surface thereof and a pressure disk, an inner rim having an annular projection on the inner surface being interposed between the hub and the pressure disk, and resilient elements, some of which are reinforced and disposed between the side surfaces of the pressure disk and the projections of the inner rim and hub; a separate resilient element being interposed between the hub and the inner surface of the annular projection of the inner rim. (cf. USSR Inventor's Certificate No. 447,305; IPC B 60B 9/12, published 1974).
The resilient elements are of unitized construction. The resilient element disposed between the hub and the inner surface of the annular projection of the inner rim is comprised of two rubber rings arranged on the hub with a certain spacing therebetween. Each resilient element interposed between the side surfaces of the pressure disk and the annular projections of the inner ring and hub is fashioned as a rubber sleeve with two metal plates vulcanized to the two sides thereof; a part of the plate engaging with the side surface of the annular projection of the inner rim is vulcanized to the corresponding rubber ring, while these rubber sleeves have holes for the passage of air and insertion of the bracing elements.
The above arrangement of the resilient elements provides required radial rigidity of the wheel and give a somewhat excessive tangential rigidity, although such wheels are well suited for locomotives travelling at a speed of up to 27.8 m/sec.
However, when employed in high-speed locomotives or locomotives in which axial loads on the rails are heavy, conditions for operation of the power drive of the locomotive in terms of torsional vibrations become less favorable.
Also, adjustment of such resilient wheels for axial rigidity is complicated, which limits their application on different types of locomotives.
The provision of holes in the rubber sleeves reduces their service life due to the generation of stresses around these holes caused by cyclic impact loads when the wheel rolls on the rail.
In addition, the ventilation ports in these wheels are arranged equidistantly in the medium portion of the annular projection of the hub and the pressure disk, which fails to ensure sufficient heat removal from the resilient elements disposed between the inner surface of the annular projection of the inner rim of the wheel and the hub thereof.